A so-called rod-type linear motor is known as a type of a linear motor to be used as a propelling means in an actuator. This rod-type linear motor includes: a stick-like magnet rod in which a plurality of magnetic poles are arrayed in a longitudinal direction thereof; and a forcer that is provided with a through-hole through which the magnet rod is inserted, and which has coil members arrayed on an inner peripheral surface thereof. In this rod-type linear motor, when drive currents are passed through the coil members, propulsion force is generated for the forcer along an axial direction of the magnet rod.
The one disclosed in WO 2007/026673 A1 is known as a linear actuator unit using the rod-type linear motor. This linear actuator unit includes: a guide shaft that is formed into a tubular shape while having a hollow portion therein, and has an opening portion formed along a longitudinal direction thereof; a slide member that is assembled to the guide shaft while interposing a large number of balls therebetween, and guides the guide shaft in an axial direction thereof; a magnet rod supported at both ends thereof in the hollow portion of the guide shaft; and a forcer that is arranged in the hollow portion of the guide shaft, constitutes a linear motor together with the magnet rod, and is joined to the slide member while interposing the opening portion therebetween.
When drive currents are passed through coil members of the forcer, the forcer is propelled along the magnet rod in the axial direction in the hollow portion of the guide shaft. As a result, the slide member joined to the forcer while interposing the opening portion of the guide shaft therebetween is propelled in the axial direction on an outside of the guide shaft, and it becomes possible to move the slide member by an arbitrary amount with respect to the guide shaft in response to the passing of the drive currents.
In the conventional linear actuator unit having the above-mentioned structure, as a result that the rod-type linear motor is housed in the hollow portion of the guide shaft, the linear motor as a thrust force generation source, and the guide shaft as a linear guiding means and the slide member are integrated with one another in an extremely compact fashion, and it becomes extremely easy to handle the linear actuator unit.    Patent Document 1: WO 2007/026673 A1